32 results about "Spatial fourier transform" patented technology

Methods and systems are disclosed of sensing an object. A first radiation is spatially modulated to generate a structured second radiation. The object is illuminated with the structured second radiation such that the object produces a third radiation in response. Apart from any spatially dependent delay, a time variation of the third radiation is spatially independent. With a single-element detector, a portion of the third radiation is detected from locations on the object simultaneously. At least one characteristic of a sinusoidal spatial Fourier-transform component of the object is estimated from a time-varying signal from the detected portion of the third radiation.

A system for producing an image using an imaging system includes a) transmitting at least one signal of energy toward an object to be imaged by using two transmitters having the same output amplitude but of an opposite sign, or by using one transmitter to perform the task; b) exciting at least one transducer element to produce limited-diffraction array beams or their square-wave approximations with two levels of quantitations for both sine and cosine functions, c) weighting the received signals spatially with limited-diffraction array beams, their square-wave approximations, or spatial Fourier transform, and d) digitizing and then transferring received signals through high-speed optical fibers to a system for image reconstructions.

An estimated frequency-wavenumber spectrum is generated by applying a first Anti-leakage Fourier transform method to aliased frequency components in temporal-transformed seismic data and applying a second Anti-leakage Fourier transform method to unaliased frequency components in the temporal-transformed seismic data. The second Anti-leakage Fourier transform method applies an absolute frequency-wavenumber spectrum extrapolated from unaliased frequencies to aliased frequencies to weight frequency-wavenumber components of the aliased frequencies. An inverse temporal and spatial Fourier transform is applied to the estimated frequency-wavenumber spectrum, generating trace interpolation of the seismic data.

The invention relates to a three-dimensional imaging sonar wave beam forming method applied to uniformly-distributed plane arrays in three-dimensional detection sonar. The method comprises the following steps: receiving and collecting time domain echo signals; carrying out time domain Fourier transform on the time domain echo signals, then judging whether the result obtained by the time domain Fourier transform meets the far-field condition or not, compensating distance influence items of a time delay calculation formula in a near-field wave beam forming expression formula, and then carrying out the next step if the result shows that the near-field wave beams are formed; directly carrying out the next step if the result shows that far-field wave beams are formed; carrying out spatial Fourier transform on row vectors of the plane arrays of the signals; carrying out spatial Fourier transform on line vectors of the plane arrays of the signals; performing a modulus on the obtained spatial two-dimensional Fourier transform result to obtain a final two-dimensional wave beam forming result.

Methods and apparatus for method for characterizing a height profile of a scattering surface relative to a fiducial plane. The scattering surface, which may be an interface between distinct solid, liquid, gaseous or plasma phases, is illuminated with substantially spatially coherent light, and light scattered by the scattering surface is collected and dispersed, such as by a grating, into zeroth- and first-order beams. A spatial Fourier transform of the zeroth- and first-order beams is created, and one of the beams is low-pass filtered. The beams are interfered at a focal plane detector to generate an interferogram, which is transformed to retrieve a spatially resolved quantitative phase image and/or an amplitude image of the scattering surface. Imaging may be performed during an etching process, and may be used to adaptively control a photoetching process in a feedback loop.

The invention discloses a finite space plane near-field acoustic holography measurement method based on spatial Fourier transform, which comprises the following steps: 1, establishing a free field andfinite space radiation sound field model based on a point sound source, and extracting complex sound pressure of a point sound source reconstruction surface in the free field and complex sound pressure data on a holographic surface in a finite space; 2, calculating a sound pressure angle spectrum of a point source reconstruction surface in a free field and a point source holographic surface in afinite space, and calculating a transfer operator G-1 of the reconstruction surface and the holographic surface; 3, measuring to obtain complex sound pressure data on the holographic surface with thereconstructed sound source in the limited space; and calculating a holographic surface sound pressure angle spectrum; 4, multiplying the holographic surface sound pressure angle spectrum in the step 3by the transfer operator G-1 in the step 2 to obtain a sound pressure angle spectrum on the reconstruction surface; and 5, performing wave number domain windowing on the sound pressure angle spectrumof the reconstruction surface; and performing Fourier inverse transformation on the windowed reconstructed sound pressure angular spectrum to obtain reconstructed surface sound pressure. According tothe method, the finite space test environment is considered, and the reconstruction precision is improved by solving the transfer operator in the free field and the finite space.

Device for the representation, in a frequency-wave number reference frame f-k, of the propagation of an ultrasound wave in a dihedral guide (1), which comprises ultrasound emitters (2) referenced by 'Ej ' with j an integer varying between 1 and N, N a strictly positive integer and ultrasound receivers (3) referenced by 'Ri ' with i an integer varying between 1 and M, M a strictly positive integer, the receivers being disposed spatially over a first segment of a straight line according to a regular pitch 'A ', which comprises means for processing the signal received by the receivers, originating from the emitters, and in which the processing means comprise means for calculating a modified discrete spatial Fourier transform, for a spatial integration variable 'x ', centred in the middle of said first segment and running through the receivers in the direction of increasing x, and for a wave vector k(x) equal to a product k.P(x), with k a constant coefficient in x and included between 0 and 2*Pi/A, and with P(x) a polynomial in x, of coefficient of degree 0 in x equal to 1 and of coefficient 'C ' of degree 1 in x such that C.A lies between -1/10 and +1/10.

The invention provides a compressor stall pre-warning signal reconstruction and identification method based on a single-path sensor signal. The method includes obtaining the pressure signal through asingle-path sensor installed in the circumferential direction of a front-stage case of a compressor; and then according to the rotation characteristic of the compressor stall pre-warning signal, simulating the output of a multi-path sensor in the circumferential direction by adopting a signal translation method, and realizing the multi-path stall pre-warning signal reconstruction of the compressor. The reconstructed multi-path stall pre-warning signal is expressed as the superposition of the torus average and the circumferential pressure disturbance in the vector form, and the circumferentialpressure disturbance vector is subjected to the spatial Fourier transform to be decomposed into the superposition of multi-order modal waves; the first-order modal amplitude is compared with the set threshold value, and the stall is considered to occur when the threshold value is exceeded, and the identification of the stall pre-warning signal is realized. A single sensor can be used to replace aplurality of sensors, so that the defect that a plurality of sensors are installed is overcome, and the method has a large engineering application value.

The invention discloses a method for obtaining dispersion characteristics and coupling impedance of a slow wave structure. Firstly, a lossless slow wave structure model to be processed is established;relevant parameters of the slow wave structure model are set; sinusoidal excitation signals are input, when the energy of the slow wave structure model is stabilized at the t0 moment, a time domain field monitor extracts electric field distribution on a field monitoring line to obtain an electric field graph, then spatial Fourier transform is carried out on the electric field graph, parameter correction is carried out, and finally the dispersion characteristic and the coupling impedance of the slow wave structure are calculated.

The present invention relates to a method for predicting the shape of a three-dimensional object which has been subjected to a diffusion process for a predetermined duration. The prediction method uses a law of vertical morphing and a law of lateral morphing. The law of lateral morphing applies to a description of the contours of different slices of a sample at standardised heights. The description of the contour of a slice is obtained by a curvilinear Fourier transform of the contour or by a two-dimensional spatial Fourier transform of a contour line approximating said contour. The present invention also relates to the manufacture of a three-dimensional object of a given material and a given nominal shape.

A two-layer hybrid solid wedged etalon was fabricated and combined with a traditional imager to make a compact computational spectrometer. The hybrid wedge was made of Nb₂O₅ and Infrasil 302 and was designed to operate from 0.4-2.4 μm. Initial demonstrations used a CMOS imager and operated from 0.4-0.9 μm with spectral resolutions<30 cm⁻¹ from single snapshots. The computational spectrometer operates similarly to a spatial Fourier Transform infrared (FTIR) spectrometer with spectral reconstruction using a non-negative least squares fitting algorithm based on analytically computed wavelength response vectors determined from extracted physical thicknesses across the entire two-dimensional wedge. This computational technique resulted in performance and spectral resolutions exceeding those that could be achieved from Fourier techniques. With an additional imaging lenses and translational scanning, the system can be converted into a hyperspectral imager.